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Testing Helps Manage Resources Efficiently

It's time to move beyond the "grab-a-sample" mentality.Accuracy of manure nutrient tests depends largely on how carefully the sample was taken. Successful nutrient management depends on how those test results are used.John Baumgartner, president, Baumgartner Environics, Inc., Olivia, MN, says there are two important questions to ask about manure test accuracy: How accurate is the lab, and how representative

Lora Duxbury-Berg | Feb 01, 1998

It's time to move beyond the "grab-a-sample" mentality.

Accuracy of manure nutrient tests depends largely on how carefully the sample was taken. Successful nutrient management depends on how those test results are used.

John Baumgartner, president, Baumgartner Environics, Inc., Olivia, MN, says there are two important questions to ask about manure test accuracy: How accurate is the lab, and how representative is the sample?

According to Baumgartner, most laboratory testing methods are highly accurate. The weight then lies on the shoulders of the producer taking the manure test sample and using those test results to be a good environmental steward.

"This is not just a 'go-out-and-grab-a-sample' situation anymore," he says. "Producers need to use a probe to get a complete sample, or take the time to agitate properly. In order to get a well-blended sample, the sample needs to be drawn as soon as the agitation stops."

In as little as 30 seconds, phosphorus can settle to the bottom of the manure containment facility resulting in a less accurate sample.

Manure testing is essential just before it is hauled, Meador says. There are no "cookie cutter" recommendations on which producers can rely. Each containment system is different, and each building is going to have different manure sampling results based on diet, waste water in the manure holding container, etc. Multiple manure containment facilities on the same farm all need to be sampled separately. Manure samples should be taken each time manure is removed from a storage facility.

Before a composite sample has been gathered, a producer should know what type of containers and instructions the laboratory requires. Producers should also be aware of turn-around time a laboratory needs before results are available. It also helps to know what type of information a producer needs.

Meador usually refers his clients to a lab that produces results in three days. This particular lab typically reports results in lb./gal.

The analysis shows total solids, moisture, total Kjeldahl nitrogen, ammonia nitrogen, organic nitrogen, phosphorus, P205 (the plant-available form of phosphorus), potassium, K20 (the potassium available to plants) calcium, magnesium, sodium, sulfur, copper, manganese, zinc and iron. The lab will report these results in lb./1,000 gal. or lb./cu. ft. for example, depending on how the producer will be applying the manure and which results will be most meaningful.

Meador doesn't do soil sampling himself, but he will look at a producer's soil sampling results to help figure out how to optimize soil nutrients and where manure needs to be utilized. To receive the most benefit from the manure application, commercial fertilizer application rates to the same land need to be reduced by the level of nutrients already available in the soil, and those provided by the applied manure.

The ideal situation would be to have a producer using soil sampling grids and using global positioning systems (GPS) to show where manure has been applied, he adds.

Meador provides a 10-part plan for the producers he works with. This plan includes figuring out how crops have depleted the nitrogen, phosphorus and potassium from previous manure applications. The important parameters for determining manure application rates include total nitrogen, ammonia nitrogen, phosphorus, and potassium.

Meador makes recommendations for spreading the manure in the field based on his knowledge of the settling characteristics of the different nutrients. For example, phosphorus tends to settle to the bottom of manure sludge, both in the pit and in the tank while being hauled. This means if a producer always applies in the same pattern, the area of the field where the tank empties every time will be higher in phosphorus.

Laboratory tests are accurate enough to help insure careful producers are good environmental stewards, he says.

John Baumgartner emphasizes the most important manure nutrient to manage is nitrogen. A carefully constructed nutrient management plan takes into account the level of nitrogen available according to soil test results, and where the nutrient-rich manure is most needed.

The soil test results will vary depending on the crops grown in the previous year. For example, if a legume crop was just raised, the decaying plant material would contribute to a nitrogen credit.

The level of nitrogen a producer may want in a particular field varies from state to state, depending on the crop to be grown and expected crop yield. A producer who is expecting150 bu./acre corn would fertilize differently than a producer expecting a higher yield.

Baumgartner's plans take into consideration whether the manure is organic or inorganic. Organic nitrogen, which is found in the solid portion of fecal material, has to go through a mineralization process and can take up to three years to be broken down completely in the soil to a form crops can use. Livestock production systems with more bedding tend to have more organic nitrogen than non-bedded systems, he says.

His clients with two-stage anaerobic lagoons who are removing the top half of the liquid manure would be getting more inorganic nitrogen, which is immediately available to crops. Consequently, this also may not leave as much nitrogen carryover for next year's crops.

Controlling Nitrates Aerobic bacteria convert ammonia in the nitrogen to nitrate, which is then more easily taken up by the plants. If manure is over-applied, excess nitrate can end up in the groundwater. If the concentration of nitrate in groundwater exceeds 10 mg./liter, the "blue baby syndrome" may result. Babies drinking nitrate-contaminated water can suffer a decreased ability for their bodies to use oxygen.

Phosphorus and potassium levels of manure applied to the soil are not usually as big a concern as nitrogen, according to Baumgartner, because both phosphorus and potassium bind tightly to soil particles and are released over time.

If a soil tests in the very high category for phosphorus, the main concern is not groundwater contamination, as much as the threat to surface water. Phosphorus in surface water serves as what Baumgartner calls a "super food" for algae. Rapid algae growth uses up the oxygen in surface water and can lead to fish kill.

"It doesn't take that much phosphorus to cause an algae bloom in surface water," he explains. Erosion control plays a key role in controlling phosphorus runoff into surface water.

Potassium hasn't been demonstrated to be a threat to either surface or groundwater, he says.

Bank Nutrients In Your Soil When explaining the importance of testing soil to know the nutrient levels before applying manure, Baumgartner suggests producers think of their soil as being like a bank. "When you apply phosphorus and postassium, what you put on that field will be there for future crop production," he says. "What your crops take off needs to be replaced to keep operating efficiently."

Baumgartner is gearing up to use Geographic Information Systems Technology and global positioning systems to help producers record how much manure they have applied and where.

Baumgartner says the manure test results should be presented in a form that can be used with a producer's soil test results. He offers formulas for converting the phosphorus value to P2O5, which is the plant-available phosphorus level expressed on soil tests (phosphorus value x 2.29=P2O5). Potassium value can be converted to K20 by taking the potassium value x 1.2=K20.

Baumgartner says manure testing can range from $25-$50, depending on the laboratory. He suggests producers have soil samples taken every three years. Soil sampling can cost from $10-$15/sample. Prices depend on the laboratory and turn-around time.

Please refer to page 22 for addresses of manure-testing laboratories as listed in the National Pork Producers Council Guide to Environmental Quality in Pork Production

When it comes to odor, some may see conflict, but Charles Gantzer, Minneapolis, MN, sees chemistry. Gantzer uses a chemistry-based approach to predicting potential odor episodes.

Based on the measured concentrations of selected odor-causing compounds in the manure, Gantzer uses computer modeling to predict odorous gas concentrations downwind of the hog facility.

The computer program considers chemical properties of various odorous gases found in stored manure, the ability of people to smell certain gases, wind spee d and weather conditions. The chemical analysis and computer program allow Gantzer to predict atmospheric concentration of odorous gases such as butyric acid and hydrogen sulfide at property lines and at the site's nearest neighbors.

By knowing the types of chemicals responsible for downwind odors, manure pit and lagoon additives can also be screened for potential effectiveness. For example, a manure additive effective in reducing hydrogen sulfide concentrations will not reduce odors caused by phenolic compounds, Gantzer says. The chemistry-based approach prevents the needless waste of time and money associated with asking an additive to do something it was not designed to do.

"Chemical and microbial manure treatments can be expensive and, in many cases, only temporary because the conditions responsible for the problem reoccur," Gantzer explains. "By periodically sampling the manure, we can determine the most effective times to re-apply the treatments."

Climate, diet and season are just some variables that affect when odors will be at their worst. Chemical analysis can help producers determine when "pre-emptive measures" might reduce or eliminate pending odor episodes, Gantzer explains.

He charges between $250-$1500 for his services. The fee is based on the size of a particular site and the number of manure storage facilities that must be analyzed.

Gantzer's models are often used when producers are seeking permits to build or expand hog units. He can help producers predict and prove odors will be within restrictions required by some states